Regional rheological differences in locomoting neutrophils

Intracellular rheology is a useful probe of the mechanisms underlying spontaneous or chemotactic locomotion and transcellular migration of leukocytes. We characterized regional rheological differences between the leading, body, and trailing regions of isolated, adherent, and spontaneously locomoting human neutrophils. We optically trapped intracellular granules and measured their displacement for 500 ms after a 100-nm step change in the trap position. Results were analyzed in terms of simple viscoelasticity and with the use of structural damping (stress relaxation follows a power law in time). Structural damping fit the data better than did viscoelasticity. Regional viscoelastic stiffness and viscosity or structural damping storage and loss moduli were all significantly lower in leading regions than in pooled body and/or trailing regions (the latter were not significantly different). Structural damping showed similar levels of elastic and dissipative stresses in body and/or trailing regions; leading regions were significantly more fluidlike (increased power law exponent). Cytoskeletal disruption with cytochalasin D or nocodazole made body and/or trailing regions ∼50% less elastic and less viscous. Cytochalasin D completely suppressed pseudopodial formation and locomotion; nocodazole had no effect on leading regions. Neither drug changed the dissipation-storage energy ratio. These results differ from those of studies of neutrophils and other cell types probed at the cell membrane via β2-integrin receptors, which suggests a distinct role for the cell cortex or focal adhesion complexes. We conclude that 1) structural damping well describes intracellular rheology, and 2) while not conclusive, the significantly more fluidlike behavior of the leading edge supports the idea that intracellular pressure may be the origin of motive force in neutrophil locomotion.

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Statistics of Single Cell Mechanics Investigated by Atomic Force Microscopy

MRS Proceedings ◽

10.1557/proc-1261-u01-08 ◽

2010 ◽

Vol 1261 ◽

Author(s):

Shinichiro Hiratsuka ◽

Yusuke Mizutani ◽

PingGen Cai ◽

Masahiko Tsuchiya ◽

Hiroshi Tokumoto ◽

...

Keyword(s):

Single Cell ◽

Power Law ◽

Force Measurement ◽

Live Cells ◽

Structural Damping ◽

Force Microscopy ◽

Atomic Force ◽

Storage And Loss Moduli ◽

Power Law Function ◽

Damping Model

AbstractWe have developed the atomic force microsocpy (AFM) to measure the complex shear modulus, G*, of a large number of cells. In the AFM technique, live cells were arranged in a micro-fabricated glass substrate under the physiological conditions, and the AFM force measurement was examined in many different cells automatically. The results shown in the previous studies revealed that the frequency-dependent G* was well fitted to the so-called structural damping model, which consists of a single power-law function with a Newtonian viscous effect. However, the detail relationship has not been understood. The aim of this study was to verify the relationship between the storage and loss moduli. As results, we found that the relation between the hysteresivity (the ratio of the storage and loss moduli) and the power-law exponent was in good agreement with the structural damping model, and the result was the same as that observed in magnetic twisting cytometry (MTC), in which cells were cultured on flat substrates. This result indicated that the AFM technique presented here becomes a useful technique for precisely measuring the statistical behavior of single cell rheology.

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Pre-stress of actin cortices is important for the viscoelastic response of living cells

10.1101/783613 ◽

2019 ◽

Author(s):

Andrea Cordes ◽

Hannes Witt ◽

Aina Gallemí-Pérez ◽

Bastian Brückner ◽

Florian Grimm ◽

...

Keyword(s):

Power Law ◽

Polymer Networks ◽

Viscoelastic Model ◽

Cell Cortex ◽

Actin Networks ◽

Viscoelastic Parameters ◽

Atomic Force ◽

Power Law Exponent ◽

Relaxation Curves ◽

Indenter Geometry

Shape, dynamics, and viscoelastic properties of eukaryotic cells are primarily governed by a thin, reversibly cross-linked actomyosin cortex located directly beneath the plasma membrane. We obtain time-dependent rheological responses of fibroblasts and MDCK II cells from deformation-relaxation curves using an atomic force microscope to access the dependence of cortex fluidity on pre-stress. We introduce a viscoelastic model that treats the cell as a composite shell and assumes that relaxation of the cortex follows a power law giving access to cortical pre-stress, area compressibility modulus, and the power law (fluidity) exponent. Cortex fluidity is modulated by interfering with myosin activity. We find that the power law exponent of the cell cortex decreases with increasing intrinsic pre-stress and area compressibility modulus, in accordance with previous finding for isolated actin networks subject to external stress. Extrapolation to zero tension returns the theoretically predicted power law exponent for transiently cross-linked polymer networks. In contrast to the widely used Hertzian mechanics, our model provides viscoelastic parameters independent of indenter geometry and compression velocity.

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A role for cytoplasmic dynein and LIS1 in directed cell movement

The Journal of Cell Biology ◽

10.1083/jcb.200310097 ◽

2003 ◽

Vol 163 (6) ◽

pp. 1205-1211 ◽

Cited By ~ 137

Author(s):

Denis L. Dujardin ◽

Lora E. Barnhart ◽

Stephanie A. Stehman ◽

Edgar R. Gomes ◽

Gregg G. Gundersen ◽

...

Keyword(s):

Total Internal Reflection ◽

Cell Movement ◽

Leading Edge ◽

Cytoplasmic Dynein ◽

Cytochalasin D ◽

Dominant Negative ◽

Cell Cortex ◽

Cell Monolayers ◽

Intracellular Movement ◽

Microtubule Reorientation

Cytoplasmic dynein has been implicated in numerous aspects of intracellular movement. We recently found dynein inhibitors to interfere with the reorientation of the microtubule cytoskeleton during healing of wounded NIH3T3 cell monolayers. We now find that dynein and its regulators dynactin and LIS1 localize to the leading cell cortex during this process. In the presence of serum, bright diffuse staining was observed in regions of active ruffling. This pattern was abolished by cytochalasin D, and was not observed in cells treated with lysophosphatidic acid, conditions which allow microtubule reorientation but not forward cell movement. Under the same conditions, using total internal reflection fluorescence microscopy, clear punctate dynein/dynactin containing structures were observed along the sides and at the tips of microtubules at the leading edge. Overexpression of dominant negative dynactin and LIS1 cDNAs or injection of antidynein antibody interfered with the rate of cell migration. Together, these results implicate a leading edge cortical pool of dynein in both early and persistent steps in directed cell movement.

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Linearity and time-scale invariance of the creep function in living cells

Journal of The Royal Society Interface ◽

10.1098/rsif.2004.0010 ◽

2004 ◽

Vol 1 (1) ◽

pp. 91-97 ◽

Cited By ~ 95

Author(s):

Guillaume Lenormand ◽

Emil Millet ◽

Ben Fabry ◽

James P. Butler ◽

Jeffrey J. Fredberg

Keyword(s):

Power Law ◽

Time Scale ◽

Relaxation Times ◽

Cell Types ◽

Creep Function ◽

Scale Invariant ◽

Time Constants ◽

Frequency Domains ◽

Power Law Exponent ◽

The Matrix

We report here the creep function measured in three cell types, after a variety of interventions, and over three time decades (from 3ms to 3.2 s). In each case the response conformed to a power law, implying that no distinct molecular relaxation times or time constants could characterize the response. These results add to a growing body of evidence that stands in contrast to widely used viscoelastic models featuring at most a few time constants. We show instead that the ability of the matrix to deform is time-scale invariant and characterized by only one parameter: the power law exponent that controls the transition between solid-like and liquid-like behaviour. Moreover, we validate linearity by comparison of measurements in the time and frequency domains.

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Cell mechanical properties of human breast carcinoma cells depend on temperature

Scientific Reports ◽

10.1038/s41598-021-90173-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Christian Aermes ◽

Alexander Hayn ◽

Tony Fischer ◽

Claudia Tanja Mierke

Keyword(s):

Mechanical Properties ◽

Power Law ◽

Cell Mechanics ◽

Cell Types ◽

Creep Response ◽

Temperature Range ◽

Myosin Filaments ◽

Cell Mechanical Properties ◽

Increasing Temperature ◽

Mcf 7

AbstractThe knowledge of cell mechanics is required to understand cellular processes and functions, such as the movement of cells, and the development of tissue engineering in cancer therapy. Cell mechanical properties depend on a variety of factors, such as cellular environments, and may also rely on external factors, such as the ambient temperature. The impact of temperature on cell mechanics is not clearly understood. To explore the effect of temperature on cell mechanics, we employed magnetic tweezers to apply a force of 1 nN to 4.5 µm superparamagnetic beads. The beads were coated with fibronectin and coupled to human epithelial breast cancer cells, in particular MCF-7 and MDA-MB-231 cells. Cells were measured in a temperature range between 25 and 45 °C. The creep response of both cell types followed a weak power law. At all temperatures, the MDA-MB-231 cells were pronouncedly softer compared to the MCF-7 cells, whereas their fluidity was increased. However, with increasing temperature, the cells became significantly softer and more fluid. Since mechanical properties are manifested in the cell’s cytoskeletal structure and the paramagnetic beads are coupled through cell surface receptors linked to cytoskeletal structures, such as actin and myosin filaments as well as microtubules, the cells were probed with pharmacological drugs impacting the actin filament polymerization, such as Latrunculin A, the myosin filaments, such as Blebbistatin, and the microtubules, such as Demecolcine, during the magnetic tweezer measurements in the specific temperature range. Irrespective of pharmacological interventions, the creep response of cells followed a weak power law at all temperatures. Inhibition of the actin polymerization resulted in increased softness in both cell types and decreased fluidity exclusively in MDA-MB-231 cells. Blebbistatin had an effect on the compliance of MDA-MB-231 cells at lower temperatures, which was minor on the compliance MCF-7 cells. Microtubule inhibition affected the fluidity of MCF-7 cells but did not have a significant effect on the compliance of MCF-7 and MDA-MB-231 cells. In summary, with increasing temperature, the cells became significant softer with specific differences between the investigated drugs and cell lines.

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Regional variation of recession flow power-law exponent

Hydrological Processes ◽

10.1002/hyp.11441 ◽

2018 ◽

Vol 32 (7) ◽

pp. 866-872 ◽

Cited By ~ 9

Author(s):

Swagat Patnaik ◽

Basudev Biswal ◽

Dasika Nagesh Kumar ◽

Bellie Sivakumar

Keyword(s):

Power Law ◽

Regional Variation ◽

Power Law Exponent ◽

Flow Power

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Effects of red grape juice polyphenols in NADPH oxidase subunit expression in human neutrophils and mononuclear blood cells

British Journal Of Nutrition ◽

10.1017/s0007114509382148 ◽

2009 ◽

Vol 102 (8) ◽

pp. 1125-1135 ◽

Cited By ~ 30

Author(s):

Alberto Dávalos ◽

Gema de la Peña ◽

Carolina C. Sánchez-Martín ◽

M. Teresa Guerra ◽

Begoña Bartolomé ◽

...

Keyword(s):

Nadph Oxidase ◽

Red Wine ◽

Grape Juice ◽

Cell Types ◽

Human Neutrophils ◽

Superoxide Anion Production ◽

Oxidase Subunit ◽

Subunit Expression ◽

Red Grape Juice ◽

Red Grape

The NADPH oxidase enzyme system is the main source of superoxide anions in phagocytic and vascular cells. NADPH oxidase-dependent superoxide generation has been found to be abnormally enhanced in several chronic diseases. Evidence is accumulating that polyphenols may have the potential to improve cardiovascular health, although the mechanism is not fully established. Consumption of concentrated red grape juice, rich in polyphenols, has been recently shown to reduce NADPH oxidase activity in circulating neutrophils from human subjects. In the present work we studied whether red grape juice polyphenols affected NADPH oxidase subunit expression at the transcription level. For this, we used human neutrophils and mononuclear cells from peripheral blood, HL-60-derived neutrophils and the endothelial cell line EA.hy926.Superoxide production was measured with 2′7′-dichlorofluorescein diacetate or lucigenin, mRNA expression by real-time RT-PCR and protein expression by Western blot. Each experiment was performed at least three times. In all cell types tested, red grape juice, dealcoholised red wine and pure polyphenols decreased superoxide anion production. Red grape juice and dealcoholised red wine selectively reduced p47phox, p22phox and gp91phox expression at both mRNA and protein levels, without affecting the expression of p67phox. Pure polyphenols, particularly quercetin, also reduced NADPH oxidase subunit expression, especially p47phox, in all cell types tested. The present results showing that red grape juice polyphenols reduce superoxide anion production provide an alternative mechanism by which consumption of grape derivatives may account for a reduction of oxidative stress associated with cardiovascular and/or inflammatory diseases related to NADPH oxidase superoxide overproduction.

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Growth Rate Exponents of Richtmyer-Meshkov Mixing Layers

Journal of Applied Mechanics ◽

10.1115/1.2164510 ◽

2005 ◽

Vol 73 (3) ◽

pp. 461-468 ◽

Cited By ~ 10

Author(s):

Timothy T. Clark ◽

Ye Zhou

Keyword(s):

Flow Field ◽

Power Law ◽

Mixing Layer ◽

Power Laws ◽

Mixing Layers ◽

Spatial Gradients ◽

Power Law Exponent ◽

Virtual Time ◽

Time Origin ◽

Density Ratios

The Richtmyer-Meshkov mixing layer is initiated by the passing of a shock over an interface between fluid of differing densities. The energy deposited during the shock passage undergoes a relaxation process during which the fluctuational energy in the flow field decays and the spatial gradients of the flow field decrease in time. This late stage of Richtmyer-Meshkov mixing layers is studied from the viewpoint of self-similarity. Analogies with weakly anisotropic turbulence suggest that both the bubble-side and spike-side widths of the mixing layer should evolve as power-laws in time, with the same power-law exponent and virtual time origin for both sides. The analogy also bounds the power-law exponent between 2∕7 and 1∕2. It is then shown that the assumption of identical power-law exponents for bubbles and spikes yields fits that are in good agreement with experiment at modest density ratios.

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Free Convective MHD Flow Past a Vertical Cone with Variable Heat and Mass Flux

Journal of Fluids ◽

10.1155/2013/405985 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

J. Prakash ◽

S. Gouse Mohiddin ◽

S. Vijaya Kumar Varma

Keyword(s):

Boundary Layer ◽

Power Law ◽

Mass Flux ◽

Numerical Study ◽

Convection Boundary Layer ◽

Vertical Cone ◽

Local Skin ◽

Surface Mass ◽

Flow Past ◽

Power Law Exponent

A numerical study of buoyancy-driven unsteady natural convection boundary layer flow past a vertical cone embedded in a non-Darcian isotropic porous regime with transverse magnetic field applied normal to the surface is considered. The heat and mass flux at the surface of the cone is modeled as a power law according to qwx=xm and qw*(x)=xm, respectively, where x denotes the coordinate along the slant face of the cone. Both Darcian drag and Forchheimer quadratic porous impedance are incorporated into the two-dimensional viscous flow model. The transient boundary layer equations are then nondimensionalized and solved by the Crank-Nicolson implicit difference method. The velocity, temperature, and concentration fields have been studied for the effect of Grashof number, Darcy number, Forchheimer number, Prandtl number, surface heat flux power-law exponent (m), surface mass flux power-law exponent (n), Schmidt number, buoyancy ratio parameter, and semivertical angle of the cone. Present results for selected variables for the purely fluid regime are compared with the published results and are found to be in excellent agreement. The local skin friction, Nusselt number, and Sherwood number are also analyzed graphically. The study finds important applications in geophysical heat transfer, industrial manufacturing processes, and hybrid solar energy systems.

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The Flavonols Quercetin, Myricetin, Kaempferol, and Galangin Inhibit the Net Oxygen Consumption by Immune Complex- Stimulated Human and Rabbit Neutrophils

Zeitschrift für Naturforschung C ◽

10.5560/znc.2012-0122 ◽

2014 ◽

Vol 69 (7-8) ◽

pp. 346-356 ◽

Cited By ~ 6

Author(s):

Andréa S. G. Figueiredo-Rinhel ◽

Everton O. L. Santos ◽

Luciana M. Kabeya ◽

Ana Elisa C. S. Azzolini ◽

Livia M. C. Simões-Ambrosio ◽

...

Keyword(s):

Oxygen Consumption ◽

Immune Complex ◽

Respiratory Burst ◽

Human Neutrophil ◽

Inflammatory Diseases ◽

Cell Types ◽

Oxygen Electrode ◽

Experimental Models ◽

Human Neutrophils ◽

Experimental Conditions

Stimulated human neutrophils exhibit increased net oxygen consumption (NOC) due to the conversion of O2 into the superoxide anion by the NADPH oxidase enzymatic complex during the respiratory burst. In several inflammatory diseases, overproduction of these oxidants causes tissue damage. The present study aims to: (a) optimize the experimental conditions used to measure the NOC in serum-opsonized zymosan (OZ)-and insoluble immune complex (i-IC)-stimulated human and rabbit neutrophils; and (b) compare the effect of four flavonols (quercetin, myricetin, kaempferol, and galangin) on this activity. We used a Clark-type oxygen electrode to measure the NOC of stimulated neutrophils. Eliciting the neutrophil respiratory burst with OZ and i-IC yielded similar maximum O2 uptake levels within the same species, but the human neutrophil NOC was almost four times higher than the rabbit neutrophil NOC. The optimal experimental conditions established for both cell types were 4·106 neutrophils mL-1, 2 mg mL-1 OZ, and 240 µg mL-1 i-IC. Upon stimulation with OZ or i-IC, the tested flavonols reduced the human and rabbit neutrophil NOC in the same order of potency - quercetin and galangin were the most and the least potent, respectively. These compounds were around four times more effective in inhibiting the rabbit as compared to the human neutrophil NOC, respectively. The four flavonols were not toxic to human or rabbit neutrophils. The experimental conditions used are suitable for both the determination of human and rabbit neutrophil NOC and for the assessment of the modulatory effects of natural compounds on these activities. The relationship between the level of NOC and the inhibitory potency of the flavonols suggests that rabbit neutrophils can be useful experimental models to predict the effect of drugs on immune complexstimulated human neutrophils.

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